Most ancient gold jewelry was solid gold. Now, cheap gold jewelry is made by plating a base matal piece with a thin layer of gold. When was this practice commonly employed?
Clarification…are you talking about gilding or about actual electroplating?
Gilding’s been around a long, long time, probably thousands of years.
Gold electroplating only dates from 1803 (warning: pdf), when Luigi Brugnatelli, a colleague of Volta , experimented with trying to deposit gold on base metal using Volta’s recently invented voltaic pile.
Archimedes of Syracuse (circa 287-212 BC) was famous for discovering the principle of hydrostatic displacement, which he used to demonstrate that a king’s crown that was supposed to be solid gold was actually only gold plated (the corrupt goldsmith was then executed by the king). So it’s been around since then, at least.
Gold-plated, or an alloy? Either one works…an alloy of gold would also weigh less than an equal volume of gold, assuming it’s not an alloy with lead or something heavier than gold. I’d always read or heard that it was alloy, rather than plating.
I don’t suppose anyone knows, actually – very little actual history is known from that long ago. Even his writings are known mostly from a compilation about 700 years later.
Given the technology of the times, I guess an alloy would be more likely. That’s easier to do than plating. And given that the crown was a golden replica of a laurel wreath, it’d be pretty hard to gold-plate that – much easier to use an alloy. (Actually, a pure gold crown seems rather unlikely anyway. Isn’t pure gold too soft for most jewelry uses? I understood most ‘gold’ jewelery was in fact an alloy with 1/6th (20 karat) to 1/3 (16 karat) non-gold.)
I was astounded when I read a book on Tutankhamen’s treasures. There was tons of gold leafing, fake gold, glass used as gems, and others. So fakes were common from the very earliest times.
As for Archimedes’s crowm, here’s a good .edu link, with sources, plating was not the problem. In fact, we can’t even be sure Archimedes even solved the problem, but the solution doesn’t seem to fit his M.O.